Properties API Jussi Pohjolainen

To store preferences • Simple API to • fetch • store • key value pairs

import java.io.*; import java.util.*; class Main { public static void main(String [] args) throws Exception { Properties prop = new Properties(); // set key and value prop.setProperty("fontSize", "24"); prop.setProperty("fontColor", "RGB(255,255,255)"); String optionalComments = "My preferences file"; prop.store(new FileWriter("./myfile.prop"), optionalComments); } }

myfile.prop #My preferences file #Sun Apr 26 10:56:55 EEST 2020 fontSize=24 fontColor=RGB(255,255,255)

Reading import java.io.*; import java.util.*; class Main { public static void main(String [] args) throws Exception { Properties prop = new Properties(); prop.load(new FileReader("./myfile.prop")); System.out.println(prop.get("fontSize")); System.out.println(prop.get("fontColor")); } }

Storing XML import java.io.*; import java.util.*; class Main { public static void main(String [] args) throws Exception { Properties prop = new Properties(); // set key and value prop.setProperty("fontSize", "24"); prop.setProperty("fontColor", "RGB(255,255,255)"); String optionalComments = "My preferences file"; prop.storeToXML(new FileOutputStream("./myfile.xml"), optionalComments); } }

myfile.xml My preferences file 24 RGB(255,255,255)

Reading import java.io.*; import java.util.*; class Main { public static void main(String [] args) throws Exception { Properties prop = new Properties(); prop.loadFromXML(new FileInputStream("./myfile.xml")); System.out.println(prop.getProperty("fontSize")); System.out.println(prop.getProperty("fontColor")); } }

Jackson

Jackson • Java classes to json mapping • External class library, add dependency • You can use Jackson to save for example preferences file

Dependency com.fasterxml.jackson.core jackson-databind 2.10.3

Pojo public class Dog { private String name; public void setName(String name) { this.name = name; } public String getName() { return this.name; } }

Main import com.fasterxml.jackson.databind.ObjectMapper; import java.io.*; class Main { public static void main(String [] args) throws Exception { Dog spot = new Dog(); spot.setName("Spot"); ObjectMapper objectMapper = new ObjectMapper(); objectMapper.writeValue(new File("./file.json"), spot); Dog temp = objectMapper.readValue(new File("./file.json"), Dog.class); System.out.println(temp.getName()); } }